PROJECT SUMMARY/ABSTRACT: Idiopathic pulmonary fibrosis (IPF) is a progressive fatal lung disease with suboptimal therapeutics. Fibroblast proliferation, migration, and fibroblast-to-myofibroblast differentiation (FMD) have been proposed as the major impetus for fibrosis progression. However, recent studies have begun to reveal great heterogeneity of fibroblasts and myofibroblasts in fibrotic lungs, which appear to contain both pro-fibrotic/pathologic fibroblasts and anti-fibrotic/reparative/regenerative fibroblasts. Thus, there is a critical need to better characterize fibroblast populations and to develop therapeutics specifically targeting pro-fibrotic fibroblasts while concomitantly promoting the expansion of anti-fibrotic fibroblasts. Dr. Saito?s recent data suggest that inhibition of histone deacetylase 8 (HDAC8) represents such a strategy. He discovered that: 1) HDAC8 knockdown in lung fibroblasts downregulates expression of genes encoding pro-proliferative/pro-fibrotic proteins while upregulating expression of genes encoding anti- migratory/anti-fibrotic proteins; and 2) treatment with an HDAC8-selective inhibitor ameliorates bleomycin- induced pulmonary fibrosis in mice, likely by activating anti-fibrotic signaling pathways. Based on these data, Dr. Saito hypothesizes that: 1) inhibition of HDAC8 ameliorates fibroblast proliferation, migration, and FMD by modifying chromatin structure and then activating transcription of anti- fibrotic genes; and 2) inhibition of HDAC8 reduces pulmonary fibrosis in vivo by expanding anti-fibrotic fibroblast subpopulations. Dr. Saito will test these hypotheses with three specific aims. In the first aim, he will define the effects of HDAC8 inhibition on fibroblast phenotype and gene regulation, using functional assays (i.e., proliferation assay, migration assay) and sequencing technologies (i.e., RNA-seq, ATAC-seq, ChIP-seq). In the second aim, he will identify cell intrinsic transcriptional effects of the HDAC8-selective inhibitor in a bleomycin-induced pulmonary fibrosis mouse model using single-cell RNA-seq, and determine the role of HDAC8 in cells promoting fibrosis resolution in vivo. In the third aim, he will assess whether mesenchymal cell- specific HDAC8 knockout mice are protected against bleomycin-induced pulmonary fibrosis and explore types of cells through which HDAC8 mediates pulmonary fibrosis. This work will be conducted at Tulane University, under the mentorship of Dr. Jay Kolls (the primary mentor), a recognized expert in genomics and lung biology, and Dr. Joseph Lasky (co-mentor), a recognized expert in pulmonary fibrosis, along with advisors who have expertise in genomics and epigenetics. With the guidance of his mentoring committee, Dr. Saito has developed a comprehensive four-year training program to develop the skills needed to become an independent investigator with expertise in genomics and epigenetics of pulmonary fibrosis. His commitment to research, strong mentorship, and the dedication of Tulane to training the next generation of scientists, will allow him to build a successful career as a physician-scientist.